In an exclusive interview with ABC, Ann McGregor, mother of the late Glee star Cory Monteith, speaks out for the first time since her son's drug overdose one year ago. The grieving mother reveals, "Until three days ago I couldn't look at a picture of Cory," adding "the loss is horrendous." Watch the interview in full below!

Cory Monteith, who portrayed 'Finn' on the FOX musical dramedy GLEE, died of a drug overdose last July. This past week, Glee cast members as well as his fans paid tribute to the fallen star on Twitter and Facebook.

Prior to his passing, Monteith starred in the film "Monte Carlo," opposite Leighton Meester, Selena Gomez and Katie Cassidy. His television credits included a lead role on the series "Kaya" and a recurring guest-star role on "Kyle XY." He also made numerous guest appearances on television shows, including "Smallville," "Supernatural," "Stargate," "Flash Gordon" and "Interns." Additionally, he starred in the 2007 television movie "Hybrid."

Monteith's film credits include "Final Destination 3," "The Invisible," "Deck the Halls" and "Whisper."